1. Field of the Invention
This invention relates to the field of power transmission in a driveline for an automotive vehicle. More particularly, it pertains to a multiple-speed final drive mechanism for use with a transmission mechanism.
2. Description of the Prior Art
To improve fuel economy and performance of a powertrain equipped with a multiple-speed transmission, attempts are being made to increase the number of forward speed ratios produced by the transmission. Adding gears broadens the span from first to top gear and reduces the size of steps between gears. Small step sizes help to maintain engine speed closer to its optimal value. The transmission delivers power smoother, and reduces the need to maintain desired engine speed by adjusting the throttle position.
Various attempts have been made to increase the number of speed ratios produced by an automatic transmission by adding an auxiliary gearset in the torque delivery path at a location either before the existing planetary gearset or between a multiple-speed planetary gearset and the final drive gearset. The auxiliary gearsets are located coaxially with the engine crankshaft, or coaxially with the output shaft. An example of the former arrangement is disclosed in U.S. application Ser. No. 08/172,964, filed Dec. 27, 1993, and assigned to the assignee of the present invention.
A principal objective of a multiple-speed axle arrangement, according to the present invention, is to reduce the overall size, weight, complexity, and cost required to produce a five speed automatic transmission.